Credence goods markets suffer from inefficiencies caused by superior information of sellers about the surplus-maximizing quality. While standard theory predicts that equal mark-up prices solve the credence goods problem if customers can verify the quality received, experimental evidence...

We study optimal direct mechanisms for a credence goods expert who can be altruistic or spiteful. The expert has private information about her distributional preferences and possibly also about her customer's needs. We introduce a method that allows the customer to offer separate contracts to...